The present invention concerns improvements made to sealing gaskets intended to be clamped between two pipework connection flanges and the invention relates more particularly to gaskets of this kind which comprise a sealing ring Including a rigid metal annular part with which are integral several radiating metal lugs capable of being folded along the contour of a support flange.
In the area of industrial pipework, in particular in the chemical and oil industries, pipelines may be constituted of sections of piping connected end to end by means of flanges between which are placed sealing gaskets. A particular feature of these gaskets is that their dimensional characteristics (internal diameter in particular) correspond with the diameter of the flanges, which in their turn correspond with the diameter of the pipe and the nominal admissible pressure. These respective dimensions may be standardised.
The result of this general arrangement is that each pipe diameter has a corresponding flange diameter and therefore gasket diameter.
Additionally, the gaskets can only be used within the limitations of a nominal pressure for which they have been designed.
Given these constraints, in order to cover a great number of different applications, a substantial range of gaskets of different diameters and withstanding different nominal pressures have to be kept available, which obliges the manufacturer and the user to maintain a bulky stock of materials in storage.
Lastly, the gaskets currently in use have other drawbacks, particularly: the impossibility of checking the characteristics of a gasket in place between the tightened flanges; the possibility of re-using a gasket which has already been used and has already been compressed; the impossibility of checking the correct centring of the gasket from the time the two flanges are brought to face each other on either side of the gasket.
The object of the Invention is thus essentially to propose a simple technical solution which can better meet the different needs of practice and which can eliminate, or at least reduce the different aforementioned drawbacks, by proposing an original structure for a sealing gasket for flanged industrial pipework which can be used for a whole range of flanges of different diameters so as to reduce the stocks of materials kept in store both by the manufacturer and by the user, which is easy to position and whose centring can be checked even on vertical flanges, which enables its characteristics to be checked after assembly between the flanges, which can no longer be re-used after dismantling, and which in the final analysis retains the mechanical and sealing characteristics of prior gaskets and involves no appreciable extra cost to manufacture.
To these ends, a sealing gasket as mentioned in the preamble is characterised, when arranged in accordance with the invention, in that, since the sealing gasket has to be able to be mounted between flanges of different transverse dimensions, the metal lugs have a length exceeding the corresponding transverse dimension of the largest flanges on which the gasket can be mounted, by means of which arrangement the lugs can be folded to conform with the exact dimension of an assembly flange so that the gasket can be appropriately supported centred by the said flange prior to the mutual assembly and tightening of the two flanges.
To be sure, sealing gaskets are already known for flanges which are fitted with radiating lugs which can be folded to about 90xc2x0 (see for example DE-U-78 35 369, DE-A-27 38 244). However, in these known gaskets, the foldable lugs are solely intended to support the gasket on a flange of given dimension and possibly to fix it to it. In no event do the lugs enable the gasket to be mounted on flanges of different diameters.
On the contrary, thanks to the particular configuration of its lugs, a gasket in accordance with the invention can be mounted equally well on a plurality of flanges of different dimensions (flanges belonging to a given dimensional range; flanges corresponding to different standardisations; etc.)
In these conditions, it is quite conceivable to constitute a gasket of diameter and mechanical characteristics appropriate to the fitting of flanges of different diameters capable of supporting pressures in a given fork. Thus, in a typical example, provision may be made for the implementation of only two different types of gaskets with the same external diameter, namely:
low-pressure gaskets for nominal pressures up to 100 bar/mm,
high-pressure gaskets for nominal pressures between 150 and 420 bar/mm.
It is desirable for the lugs to comprise reference markers corresponding to the prespecified dimensions of flanges so as to facilitate their folding to the exact dimension for the purpose of correct centring of the gasket on the flanges during its installation.
In a practical version, the radiating lugs are four in number, approximately diametrically opposite two by two and mutually offset angularly by about 90xc2x0.
Lastly, it is advantageous for at least one radiating lug to comprise particularly alphanumeric and/or colour marks, to identify the category of gasket, these marks being affixed to the end of the lug which protrudes and remains visible outside the assembled flanges.
Such an arrangement of radiating lugs, which are to advantage added by welding onto the metal annular part of the gasket, offers the considerable advantage of leaving intact the part forming the actual sealing gasket: this can therefore continue to be constituted like a prior gasket of the same type and continue to have the same functional characteristics.
In part, the arrangements specific to the invention can be applied to gaskets of different types, i.e. gaskets in which the above-mentioned rigid annular part constitutes a rigid core of the gasket, or also to gaskets in which the rigid annular part is a rigid ring externally surrounding the gasket and being of smaller thickness than the latter: gaskets provided in accordance with the invention can thus retain the anticrush component.
In the final analysis, the arrangements in accordance with the invention enable:
simplified and accelerated positioning of the gasket on a flange, even one placed vertically,
error reduction when choosing which gaskets to fit,
simplification and reduction of manufacturing and storage costs for the manufacturer,
simplification and reduction of the range of products to use and reduction in storage cost for the user.
The arrangements of the invention find a more specifically advantageous, although not exclusive, application, in so-called xe2x80x9ccoated metal jacketed gaskets which comprise an annular filler forming a core surrounded by a metal sheath which is coated, on its two main opposite faces, with respective layers of a non-stick material, the said gasket being able if necessary to be fitted with an external metal ring.
It will also be noted that the implementation of the arrangements of the invention does not depend in any way on the structure of the internal contour of the gasket, particularly on the presence or absence of an internal metal centring and/or anti-crush ring.